1. Field of the Invention
This invention relates to internal combustion engines, and, more particularly, to internal combustion engines having dual pistons for self-supercharging characteristics.
2. Description of the Prior Art
Internal combustion engines have used dual pistons for various purposes. By "dual" as used in the present application is meant two pistons coaxially aligned on a common piston rod or connecting rod. An early example of a dual piston engine is disclosed in U.S. Pat. No. 758,189, dated Apr. 26, 1904. The U.S. Pat. No. 758,189 discloses a pair of pistons in which the bottom piston is employed for cushioning and for scavaging purposes. The combustion chamber for the engine is above the top piston, and the bottom of the two pistons are not used.
U.S. Pat. No. 912,012, dated Feb. 9, 1909, also discloses a dual piston engine in which two combustion chambers are used on top of the two pistons. The bottom of the top piston is used to charge both combustion chambers. No supercharging is employed with either the U.S. Pat. No. 912,012 or with the previously discussed U.S. Pat. No. 758,189.
Another type of dual piston engine is disclosed in U.S. Pat. No. 1,504,957, dated Aug. 12, 1924. The U.S. Pat. No. 1,504,957 uses the bottom piston for scavenging and cushioning purposes, not dissimilar to that disclosed in the U.S. Pat. No. 758,189.
In U.S. Pat. No. 1,983,237, dated Dec. 4, 1934, the bottom piston of the dual piston engine is used primarily for scavenging purposes.
In U.S. Pat. No. 2,303,966, dated Dec. 1, 1942, a dual piston engine is disclosed in which supercharging is accomplished from the bottom of the top piston. Only a single combustion chamber is used, and the combustion chamber is located above the top piston. Sleeve valves are used to control the inlet and outlet of a fuel-air mixture from below and above the top piston.
In all of the above-described patents, excep the U.S. Pat. No. 758,189, which discloses a diesel type internal combustion engine, carburetion is employed at the air intake, and before any supercharging, regardless of the path of the air or fuel-air mixture. That is, the carburetion is ahead of any supercharging that is accomplished by means of the dual piston arrangement. Two inherent problems are involved in such an arrangement. The first problem is a decrease in efficiency due to the pumping of the fuel vapors. The second problem is that the presence of the fuel interferes with the lubrication of the pistons by washing out lubricating oil. Those two problems are overcome by the arrangement of the present invention in which the carburetion is placed between the combustion chamber and the air inlet, or after the supercharger. Thus there is an increase in efficiency of the supercharging or air pumping by eliminating the pumping of the fuel vapors and there is no interference with the lubrication of the pistons.